Fixes for GPU hang, null dereference, suspend-resume, power consumption, and use-after-free.

- Program mocs:63 for cache eviction on gen9 (Chris)
 - Protect context lifetime with RCU (Chris)
 - Split the breadcrumb spinlock between global and contexts (Chris)
 - Retain default context state across shrinking (Venkata)
 - Limit frequency drop to RPe on parking (Chris)
 - Return earlier from intel_modeset_init() without display (Jani)
 - Defer initial modeset until after GGTT is initialized (Chris)
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Merge tag 'drm-intel-fixes-2020-12-03' of git://anongit.freedesktop.org/drm/drm-intel into drm-fixes

Fixes for GPU hang, null dereference, suspend-resume, power consumption, and use-after-free.

- Program mocs:63 for cache eviction on gen9 (Chris)
- Protect context lifetime with RCU (Chris)
- Split the breadcrumb spinlock between global and contexts (Chris)
- Retain default context state across shrinking (Venkata)
- Limit frequency drop to RPe on parking (Chris)
- Return earlier from intel_modeset_init() without display (Jani)
- Defer initial modeset until after GGTT is initialized (Chris)

Signed-off-by: Dave Airlie <airlied@redhat.com>

From: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201203134705.GA1575873@intel.com

drivers/gpu/drm/i915/display/intel_display.c

@@ -18021,16 +18021,6 @@ int intel_modeset_init_nogem(struct drm_i915_private *i915)
 	if (!HAS_GMCH(i915))
 		sanitize_watermarks(i915);
 
-	/*
-	 * Force all active planes to recompute their states. So that on
-	 * mode_setcrtc after probe, all the intel_plane_state variables
-	 * are already calculated and there is no assert_plane warnings
-	 * during bootup.
-	 */
-	ret = intel_initial_commit(dev);
-	if (ret)
-		drm_dbg_kms(&i915->drm, "Initial commit in probe failed.\n");
-
 	return 0;
 }
 
@@ -18039,11 +18029,21 @@ int intel_modeset_init(struct drm_i915_private *i915)
 {
 	int ret;
 
-	intel_overlay_setup(i915);
-
 	if (!HAS_DISPLAY(i915))
 		return 0;
 
+	/*
+	 * Force all active planes to recompute their states. So that on
+	 * mode_setcrtc after probe, all the intel_plane_state variables
+	 * are already calculated and there is no assert_plane warnings
+	 * during bootup.
+	 */
+	ret = intel_initial_commit(&i915->drm);
+	if (ret)
+		return ret;
+
+	intel_overlay_setup(i915);
+
 	ret = intel_fbdev_init(&i915->drm);
 	if (ret)
 		return ret;

drivers/gpu/drm/i915/gt/intel_breadcrumbs.c

@@ -101,18 +101,37 @@ static void __intel_breadcrumbs_disarm_irq(struct intel_breadcrumbs *b)
 	intel_gt_pm_put_async(b->irq_engine->gt);
 }
 
+static void intel_breadcrumbs_disarm_irq(struct intel_breadcrumbs *b)
+{
+	spin_lock(&b->irq_lock);
+	if (b->irq_armed)
+		__intel_breadcrumbs_disarm_irq(b);
+	spin_unlock(&b->irq_lock);
+}
+
 static void add_signaling_context(struct intel_breadcrumbs *b,
 				  struct intel_context *ce)
 {
-	intel_context_get(ce);
-	list_add_tail(&ce->signal_link, &b->signalers);
+	lockdep_assert_held(&ce->signal_lock);
+
+	spin_lock(&b->signalers_lock);
+	list_add_rcu(&ce->signal_link, &b->signalers);
+	spin_unlock(&b->signalers_lock);
 }
 
-static void remove_signaling_context(struct intel_breadcrumbs *b,
+static bool remove_signaling_context(struct intel_breadcrumbs *b,
 				     struct intel_context *ce)
 {
-	list_del(&ce->signal_link);
-	intel_context_put(ce);
+	lockdep_assert_held(&ce->signal_lock);
+
+	if (!list_empty(&ce->signals))
+		return false;
+
+	spin_lock(&b->signalers_lock);
+	list_del_rcu(&ce->signal_link);
+	spin_unlock(&b->signalers_lock);
+
+	return true;
 }
 
 static inline bool __request_completed(const struct i915_request *rq)
@@ -175,6 +194,8 @@ static void add_retire(struct intel_breadcrumbs *b, struct intel_timeline *tl)
 
 static bool __signal_request(struct i915_request *rq)
 {
+	GEM_BUG_ON(test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags));
+
 	if (!__dma_fence_signal(&rq->fence)) {
 		i915_request_put(rq);
 		return false;
@@ -195,15 +216,12 @@ static void signal_irq_work(struct irq_work *work)
 	struct intel_breadcrumbs *b = container_of(work, typeof(*b), irq_work);
 	const ktime_t timestamp = ktime_get();
 	struct llist_node *signal, *sn;
-	struct intel_context *ce, *cn;
-	struct list_head *pos, *next;
+	struct intel_context *ce;
 
 	signal = NULL;
 	if (unlikely(!llist_empty(&b->signaled_requests)))
 		signal = llist_del_all(&b->signaled_requests);
 
-	spin_lock(&b->irq_lock);
-
 	/*
 	 * Keep the irq armed until the interrupt after all listeners are gone.
 	 *
@@ -229,47 +247,44 @@ static void signal_irq_work(struct irq_work *work)
 	 * interrupt draw less ire from other users of the system and tools
 	 * like powertop.
 	 */
-	if (!signal && b->irq_armed && list_empty(&b->signalers))
-		__intel_breadcrumbs_disarm_irq(b);
+	if (!signal && READ_ONCE(b->irq_armed) && list_empty(&b->signalers))
+		intel_breadcrumbs_disarm_irq(b);
 
-	list_for_each_entry_safe(ce, cn, &b->signalers, signal_link) {
-		GEM_BUG_ON(list_empty(&ce->signals));
+	rcu_read_lock();
+	list_for_each_entry_rcu(ce, &b->signalers, signal_link) {
+		struct i915_request *rq;
 
-		list_for_each_safe(pos, next, &ce->signals) {
-			struct i915_request *rq =
-				list_entry(pos, typeof(*rq), signal_link);
+		list_for_each_entry_rcu(rq, &ce->signals, signal_link) {
+			bool release;
 
-			GEM_BUG_ON(!check_signal_order(ce, rq));
 			if (!__request_completed(rq))
 				break;
 
+			if (!test_and_clear_bit(I915_FENCE_FLAG_SIGNAL,
+						&rq->fence.flags))
+				break;
+
 			/*
 			 * Queue for execution after dropping the signaling
 			 * spinlock as the callback chain may end up adding
 			 * more signalers to the same context or engine.
 			 */
-			clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
+			spin_lock(&ce->signal_lock);
+			list_del_rcu(&rq->signal_link);
+			release = remove_signaling_context(b, ce);
+			spin_unlock(&ce->signal_lock);
+
 			if (__signal_request(rq))
 				/* We own signal_node now, xfer to local list */
 				signal = slist_add(&rq->signal_node, signal);
-		}
 
-		/*
-		 * We process the list deletion in bulk, only using a list_add
-		 * (not list_move) above but keeping the status of
-		 * rq->signal_link known with the I915_FENCE_FLAG_SIGNAL bit.
-		 */
-		if (!list_is_first(pos, &ce->signals)) {
-			/* Advance the list to the first incomplete request */
-			__list_del_many(&ce->signals, pos);
-			if (&ce->signals == pos) { /* now empty */
+			if (release) {
 				add_retire(b, ce->timeline);
-				remove_signaling_context(b, ce);
+				intel_context_put(ce);
 			}
 		}
 	}
-
-	spin_unlock(&b->irq_lock);
+	rcu_read_unlock();
 
 	llist_for_each_safe(signal, sn, signal) {
 		struct i915_request *rq =
@@ -298,14 +313,15 @@ intel_breadcrumbs_create(struct intel_engine_cs *irq_engine)
 	if (!b)
 		return NULL;
 
-	spin_lock_init(&b->irq_lock);
+	b->irq_engine = irq_engine;
+
+	spin_lock_init(&b->signalers_lock);
 	INIT_LIST_HEAD(&b->signalers);
 	init_llist_head(&b->signaled_requests);
 
+	spin_lock_init(&b->irq_lock);
 	init_irq_work(&b->irq_work, signal_irq_work);
 
-	b->irq_engine = irq_engine;
-
 	return b;
 }
 
@@ -347,9 +363,9 @@ void intel_breadcrumbs_free(struct intel_breadcrumbs *b)
 	kfree(b);
 }
 
-static void insert_breadcrumb(struct i915_request *rq,
-			      struct intel_breadcrumbs *b)
+static void insert_breadcrumb(struct i915_request *rq)
 {
+	struct intel_breadcrumbs *b = READ_ONCE(rq->engine)->breadcrumbs;
 	struct intel_context *ce = rq->context;
 	struct list_head *pos;
 
@@ -371,6 +387,7 @@ static void insert_breadcrumb(struct i915_request *rq,
 	}
 
 	if (list_empty(&ce->signals)) {
+		intel_context_get(ce);
 		add_signaling_context(b, ce);
 		pos = &ce->signals;
 	} else {
@@ -396,8 +413,9 @@ static void insert_breadcrumb(struct i915_request *rq,
 				break;
 		}
 	}
-	list_add(&rq->signal_link, pos);
+	list_add_rcu(&rq->signal_link, pos);
 	GEM_BUG_ON(!check_signal_order(ce, rq));
+	GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags));
 	set_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
 
 	/*
@@ -410,7 +428,7 @@ static void insert_breadcrumb(struct i915_request *rq,
 
 bool i915_request_enable_breadcrumb(struct i915_request *rq)
 {
-	struct intel_breadcrumbs *b;
+	struct intel_context *ce = rq->context;
 
 	/* Serialises with i915_request_retire() using rq->lock */
 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags))
@@ -425,67 +443,30 @@ bool i915_request_enable_breadcrumb(struct i915_request *rq)
 	if (!test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags))
 		return true;
 
-	/*
-	 * rq->engine is locked by rq->engine->active.lock. That however
-	 * is not known until after rq->engine has been dereferenced and
-	 * the lock acquired. Hence we acquire the lock and then validate
-	 * that rq->engine still matches the lock we hold for it.
-	 *
-	 * Here, we are using the breadcrumb lock as a proxy for the
-	 * rq->engine->active.lock, and we know that since the breadcrumb
-	 * will be serialised within i915_request_submit/i915_request_unsubmit,
-	 * the engine cannot change while active as long as we hold the
-	 * breadcrumb lock on that engine.
-	 *
-	 * From the dma_fence_enable_signaling() path, we are outside of the
-	 * request submit/unsubmit path, and so we must be more careful to
-	 * acquire the right lock.
-	 */
-	b = READ_ONCE(rq->engine)->breadcrumbs;
-	spin_lock(&b->irq_lock);
-	while (unlikely(b != READ_ONCE(rq->engine)->breadcrumbs)) {
-		spin_unlock(&b->irq_lock);
-		b = READ_ONCE(rq->engine)->breadcrumbs;
-		spin_lock(&b->irq_lock);
-	}
-
-	/*
-	 * Now that we are finally serialised with request submit/unsubmit,
-	 * [with b->irq_lock] and with i915_request_retire() [via checking
-	 * SIGNALED with rq->lock] confirm the request is indeed active. If
-	 * it is no longer active, the breadcrumb will be attached upon
-	 * i915_request_submit().
-	 */
+	spin_lock(&ce->signal_lock);
 	if (test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags))
-		insert_breadcrumb(rq, b);
-
-	spin_unlock(&b->irq_lock);
+		insert_breadcrumb(rq);
+	spin_unlock(&ce->signal_lock);
 
 	return true;
 }
 
 void i915_request_cancel_breadcrumb(struct i915_request *rq)
 {
-	struct intel_breadcrumbs *b = rq->engine->breadcrumbs;
+	struct intel_context *ce = rq->context;
+	bool release;
 
-	/*
-	 * We must wait for b->irq_lock so that we know the interrupt handler
-	 * has released its reference to the intel_context and has completed
-	 * the DMA_FENCE_FLAG_SIGNALED_BIT/I915_FENCE_FLAG_SIGNAL dance (if
-	 * required).
-	 */
-	spin_lock(&b->irq_lock);
-	if (test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags)) {
-		struct intel_context *ce = rq->context;
+	if (!test_and_clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags))
+		return;
 
-		list_del(&rq->signal_link);
-		if (list_empty(&ce->signals))
-			remove_signaling_context(b, ce);
+	spin_lock(&ce->signal_lock);
+	list_del_rcu(&rq->signal_link);
+	release = remove_signaling_context(rq->engine->breadcrumbs, ce);
+	spin_unlock(&ce->signal_lock);
+	if (release)
+		intel_context_put(ce);
 
-		clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
-		i915_request_put(rq);
-	}
-	spin_unlock(&b->irq_lock);
+	i915_request_put(rq);
 }
 
 static void print_signals(struct intel_breadcrumbs *b, struct drm_printer *p)
@@ -495,18 +476,17 @@ static void print_signals(struct intel_breadcrumbs *b, struct drm_printer *p)
 
 	drm_printf(p, "Signals:\n");
 
-	spin_lock_irq(&b->irq_lock);
-	list_for_each_entry(ce, &b->signalers, signal_link) {
-		list_for_each_entry(rq, &ce->signals, signal_link) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(ce, &b->signalers, signal_link) {
+		list_for_each_entry_rcu(rq, &ce->signals, signal_link)
 			drm_printf(p, "\t[%llx:%llx%s] @ %dms\n",
 				   rq->fence.context, rq->fence.seqno,
 				   i915_request_completed(rq) ? "!" :
 				   i915_request_started(rq) ? "*" :
 				   "",
 				   jiffies_to_msecs(jiffies - rq->emitted_jiffies));
-		}
 	}
-	spin_unlock_irq(&b->irq_lock);
+	rcu_read_unlock();
 }
 
 void intel_engine_print_breadcrumbs(struct intel_engine_cs *engine,

drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h

@@ -29,18 +29,16 @@
  * the overhead of waking that client is much preferred.
  */
 struct intel_breadcrumbs {
-	spinlock_t irq_lock; /* protects the lists used in hardirq context */
-
 	/* Not all breadcrumbs are attached to physical HW */
 	struct intel_engine_cs *irq_engine;
 
+	spinlock_t signalers_lock; /* protects the list of signalers */
 	struct list_head signalers;
 	struct llist_head signaled_requests;
 
+	spinlock_t irq_lock; /* protects the interrupt from hardirq context */
 	struct irq_work irq_work; /* for use from inside irq_lock */
-
 	unsigned int irq_enabled;
-
 	bool irq_armed;
 };
 

drivers/gpu/drm/i915/gt/intel_context.c

@@ -25,9 +25,16 @@ static struct intel_context *intel_context_alloc(void)
 	return kmem_cache_zalloc(global.slab_ce, GFP_KERNEL);
 }
 
+static void rcu_context_free(struct rcu_head *rcu)
+{
+	struct intel_context *ce = container_of(rcu, typeof(*ce), rcu);
+
+	kmem_cache_free(global.slab_ce, ce);
+}
+
 void intel_context_free(struct intel_context *ce)
 {
-	kmem_cache_free(global.slab_ce, ce);
+	call_rcu(&ce->rcu, rcu_context_free);
 }
 
 struct intel_context *
@@ -356,8 +363,7 @@ static int __intel_context_active(struct i915_active *active)
 }
 
 void
-intel_context_init(struct intel_context *ce,
-		   struct intel_engine_cs *engine)
+intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)
 {
 	GEM_BUG_ON(!engine->cops);
 	GEM_BUG_ON(!engine->gt->vm);
@@ -373,7 +379,8 @@ intel_context_init(struct intel_context *ce,
 
 	ce->vm = i915_vm_get(engine->gt->vm);
 
-	INIT_LIST_HEAD(&ce->signal_link);
+	/* NB ce->signal_link/lock is used under RCU */
+	spin_lock_init(&ce->signal_lock);
 	INIT_LIST_HEAD(&ce->signals);
 
 	mutex_init(&ce->pin_mutex);

drivers/gpu/drm/i915/gt/intel_context_types.h

@@ -25,6 +25,7 @@ DECLARE_EWMA(runtime, 3, 8);
 struct i915_gem_context;
 struct i915_gem_ww_ctx;
 struct i915_vma;
+struct intel_breadcrumbs;
 struct intel_context;
 struct intel_ring;
 
@@ -44,7 +45,16 @@ struct intel_context_ops {
 };
 
 struct intel_context {
-	struct kref ref;
+	/*
+	 * Note: Some fields may be accessed under RCU.
+	 *
+	 * Unless otherwise noted a field can safely be assumed to be protected
+	 * by strong reference counting.
+	 */
+	union {
+		struct kref ref; /* no kref_get_unless_zero()! */
+		struct rcu_head rcu;
+	};
 
 	struct intel_engine_cs *engine;
 	struct intel_engine_cs *inflight;
@@ -54,8 +64,15 @@ struct intel_context {
 	struct i915_address_space *vm;
 	struct i915_gem_context __rcu *gem_context;
 
-	struct list_head signal_link;
-	struct list_head signals;
+	/*
+	 * @signal_lock protects the list of requests that need signaling,
+	 * @signals. While there are any requests that need signaling,
+	 * we add the context to the breadcrumbs worker, and remove it
+	 * upon completion/cancellation of the last request.
+	 */
+	struct list_head signal_link; /* Accessed under RCU */
+	struct list_head signals; /* Guarded by signal_lock */
+	spinlock_t signal_lock; /* protects signals, the list of requests */
 
 	struct i915_vma *state;
 	struct intel_ring *ring;

drivers/gpu/drm/i915/gt/intel_mocs.c

@@ -131,7 +131,19 @@ static const struct drm_i915_mocs_entry skl_mocs_table[] = {
 	GEN9_MOCS_ENTRIES,
 	MOCS_ENTRY(I915_MOCS_CACHED,
 		   LE_3_WB | LE_TC_2_LLC_ELLC | LE_LRUM(3),
-		   L3_3_WB)
+		   L3_3_WB),
+
+	/*
+	 * mocs:63
+	 * - used by the L3 for all of its evictions.
+	 *   Thus it is expected to allow LLC cacheability to enable coherent
+	 *   flows to be maintained.
+	 * - used to force L3 uncachable cycles.
+	 *   Thus it is expected to make the surface L3 uncacheable.
+	 */
+	MOCS_ENTRY(63,
+		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_1_UC)
 };
 
 /* NOTE: the LE_TGT_CACHE is not used on Broxton */

drivers/gpu/drm/i915/gt/intel_rps.c

@@ -883,6 +883,10 @@ void intel_rps_park(struct intel_rps *rps)
 		adj = -2;
 	rps->last_adj = adj;
 	rps->cur_freq = max_t(int, rps->cur_freq + adj, rps->min_freq);
+	if (rps->cur_freq < rps->efficient_freq) {
+		rps->cur_freq = rps->efficient_freq;
+		rps->last_adj = 0;
+	}
 
 	GT_TRACE(rps_to_gt(rps), "park:%x\n", rps->cur_freq);
 }

drivers/gpu/drm/i915/gt/shmem_utils.c

@@ -103,10 +103,13 @@ static int __shmem_rw(struct file *file, loff_t off,
 			return PTR_ERR(page);
 
 		vaddr = kmap(page);
-		if (write)
+		if (write) {
 			memcpy(vaddr + offset_in_page(off), ptr, this);
-		else
+			set_page_dirty(page);
+		} else {
 			memcpy(ptr, vaddr + offset_in_page(off), this);
+		}
+		mark_page_accessed(page);
 		kunmap(page);
 		put_page(page);
 

drivers/gpu/drm/i915/i915_request.h

@@ -177,10 +177,8 @@ struct i915_request {
 	struct intel_ring *ring;
 	struct intel_timeline __rcu *timeline;
 
-	union {
-		struct list_head signal_link;
-		struct llist_node signal_node;
-	};
+	struct list_head signal_link;
+	struct llist_node signal_node;
 
 	/*
 	 * The rcu epoch of when this request was allocated. Used to judiciously